Starship Troopers...
Seems that plenty of you have seen the movie, but trust me when I tell you the book was better.
I can't see one, or many, of these spiders posing a threat to a squad of Mobile Infantry. In the book they had some serious combat suits, more Mech Warrior than the rubber helmet things depicted in the movie.
Plus, in the book their weapons were somewhat effective, and they had many more of them to play with.
I've always felt that spiders tend to burn rather nicely, so maybe all we need is a strategically placed molotov or flamethrower hit. If you can deliver enough energy to flash boil the innards, then a 26cm thick armored shell would just serve to build up the pressure until you could get a really entertaining explosion. For that we'd probably need some airbourne lasers.
Then again a shaped charge that can punch through 26cm of rock (seems like that'd be harder than spider) isn't very big at all. I bet you could attach the charge, deto, and ignition mechanism to a decently sized arrow and really give the big game hunters a way to entertain themselves. They all love to pretend they're Rambo.